Friday, August 24, 2007

The carpool lane

One of my early blog posts was a plea for California sponsored road safety infomercials. Simple things make a difference on the roads. We, in the Bay Area, can learn a thing or two about traffic efficiency from the South.

  • Take for example the carpool lane, officially called High Occupancy Vehicle (HOV) lane. Typically one needs to have 2 or more people in the car to ride int he carpool lane. A lot of rubber necking starts when cars from the carpool lane need to cross over to take an exit. Building a HOV specific off-ramp overpass does pay off. Such changes to the high way 101-85 merge in Mountain View solved a lot problems. On the other hand, the 101 South commute through San Jose is hampered by two merges: 101-87 and 101-880. In both cases, car pool riders need to cross all lanes to take the exit.
  • Weaving in and out of the carpool can be avoided by creating small separators between the lanes. Highway 5 near Rancho Bernardo is a great example of how traffic flow is encouraged by limiting when people can get in and out of the HOV lane.
  • In the Bay Area, the HOV lane rules apply between 6-9am and 3-7pm. A look outside my office shows that the traffic continues well beyond 9am, and starts as early as 1-2pm. Reward commuters by making the HOV lanes 24/7. (LA Times: Car pool lane revolution)
  • Traffic lights regulating the inflow to the freeway is a great idea. However, in the Bay Area, only one car is allowed to advance per green light. In San Diego, the traffic flow is smoother and stop and go traffic is reduced by allowing 2 or 3 cars to enter the high way per green light.

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